I have a spare (e.g. 'expendable') Netgear EX6130 WiFi Extender and I have put it in my garage so I can get internet when I'm working out there. I've configured it the way I want and that all works apart from a very poor uplink WiFi connection to the ADSL router in the house.
For several reasons I'm not able to lay an Ethernet cable out to the garage.
The WiFi signal has a brick wall and a sheet steel garage door to get through. It nearly works, but the signal drops out a lot and I think the garage door is the primary culprit, because the connection is about 40% better when the door is open. I need to circumvent the door somehow!
The new WiFI hotspot provided by the extender is very strong and reaches everywhere I need it to get to. It's just this bottleneck link back to the house I want to solve.
The Question: I am wondering if I could swap the Netgear's crappy built-in antennas for a pair of mag-mount WiFi antennas (with SMA connectors and 2 meter long coax cables). This means I can run the coax through the wall of the garage and place the antennas a couple of meters apart on the roof of the garage (there's a magnetic steel strip on the roof that holds down the waterproof membrane) I can stick the antennas to that metal as a ground plane. This would neatly side-step the steel door I believe.
I've already taken the device apart to see if it has U.FL antenna connectors (it does), and I have some U.FL to SMA connectors ready.
Is this a bad idea? Is this likely to destroy the RF stage of the WiFi transceiver? One one hand I know that antennas need to be compatible with a transceiver, but on the other hand the Netgear will have the cheapest possible antennas built-in and will probably not be the best way to get optimum WiFi signal. I have no budget, I'm having to use parts at my immediate disposal.
I know I could just try it but I don't want to risk destroying a perfectly good device on a whim.
Any opinions welcome.

